These studies are being conducted to evaluate the hypothesis that benchmark dose/benchmark doselevel (BMD/BMDL) analyses of transcriptional changes in the adult rat liver following short term oral exposure to a chemical will produce similar (if not slightly lower) points of departure compared to BMD/BMDL analyses of apical end-points. This approach may be useful in comparing classes of compounds and providing quantitative data to inform risk assessments. Keywords: toxicity, high throughput transcriptomics, cancer genomics